The term avermectin (previously referred to as C-076) is used to describe a series of compounds isolated from the fermentation broth of an avermectin-producing strain of Streptomyces avermitilis and derivatives thereof. The morphological characteristics of the culture are completely described in U.S. Pat. No. 4,310,519. The avermectin compounds are a series of macrolides, each of which is substituted at the 13 position with a 4-(.alpha.-L-oleandrosyl)-.alpha.-L-oleandrose group. The avermectin compounds and the derivatives of this invention have a very high degree of anthelmintic and anti-parasitic activity.
The avermectin series of compounds isolated from the fermentation broth have the following structure: ##STR1## wherein R.sub.4 is the 4'.alpha.-(L-oleandrosyl)-.alpha.-L-oleandrosyloxy group of the structure ##STR2## and wherein A at the 22,23 position indicates a single or a double bond;
R.sub.1 is a hydrogen or hydroxy and is hydroxy only when A indicates a single bond; PA1 R.sub.2 is iso-propyl or sec-butyl; and PA1 R.sub.3 is methoxy or hydroxy. PA1 (1) a single bond and wherein R.sub.1 is PA1 (2) a double bond and R.sub.1 is absent; PA1 (1) C.sub.1-4 alkyl, PA1 (2) substituted C.sub.1-4 alkyl with 1 to 3 substituents selected from C.sub.4-6 cycloalkyl, phenyl, and halo, especially fluoro, PA1 (3) alpha-branched C.sub.3-8 alkyl, especially isopropyl or sec-butyl, PA1 (4) C.sub.2-8 alkenyl, especially an alpha-branched C.sub.3-8 alkenyl group, PA1 (5) C.sub.2-6 alkynyl, PA1 (6) C.sub.1-6 alkoxy C.sub.1-6 alkyl, PA1 (7) C.sub.1-6 alkylthio C.sub.1-6 alkyl, PA1 (8) C.sub.4-6 cycloalkyl or C.sub.4-6 cycloalkenyl either unsubstituted or substituted with 1 to 3 substituents selected from PA1 (9) 3 to 6 membered nitrogen, oxygen or sulfur containing heterocycle, saturated or unsaturated, either unsubstituted or substituted with 1 to 3 substituents selected from PA1 (10) phenyl, either substituted or unsubstituted with 1 to 3 substituents selected from PA1 (1) hydroxy, PA1 (2) C.sub.1-6 alkoxy, PA1 (3) C.sub.2-6 alkanoyloxy, PA1 (4) oxo, or PA1 (5) oximino; PA1 (1) S(O).sub.n R.sub.6 wherein n is 0, 1 or 2, PA1 (2) SCOR.sub.6, or PA1 (3) iodo; PA1 (1) hydrogen, PA1 (2) C.sub.1-8 alkyl either straight or branched chain and either unsubstituted or substituted with 1-3 substitutents selected from PA1 (3) C.sub.2-8 alkanoyl either unsubstituted or substituted with 1-3 substitutents selected from PA1 (4) C.sub.3-8 cycloalkyl, either unsubstituted or substituted with 1-3 substitutents selected from PA1 (5) nicotinoyl. PA1 (1) S(O).sub.n R.sub.6 wherein n is 0, 1 or 2, or PA1 (2) SCOR.sub.6 ; PA1 (1) hydrogen, PA1 (2) C.sub.1-4 alkyl either straight or branched chain and either unsubstituted or substituted with 1-3 substitutents selected from PA1 (3) C.sub.2-5 alkanoyl either unsubstituted or substituted with 1-3 substitutents selected from PA1 (1) hydroxy, PA1 (2) C.sub.1-2 alkoxy, PA1 (3) amino, PA1 (4) acetylamino, PA1 (5) C.sub.1-2 alkylamino, and PA1 (6) dimethylamino. PA1 (7) halo
There are eight different avermectin natural product compounds and they are given the designations A1a, A1b, A2a, A2b, B1a, B1b, B2a, and B2b based upon the structure of the individual compounds. In the foregoing structural formula, the individual avermectin compounds are as set forth below.
______________________________________ (The R group is 4'-.alpha.-(L-oleandrosyl)- .alpha.-L-oleandrosyloxy.) (A) R.sub.1 R.sub.2 R.sub.3 ______________________________________ A1a double bond -- sec-butyl --OCH.sub.3 A1b double bond -- iso-propyl --OCH.sub.3 A2a single bond --OH sec-butyl --OCH.sub.3 A2b single bond --OH iso-propyl --OCH.sub.3 B1a double bond -- sec-butyl --OH B1b double bond -- iso-propyl --OH B2a single bond --OH sec-butyl --OH B2b single bond --OH iso-propyl --OH ______________________________________
The avermectin compounds are generally isolated as mixtures of a and b components. Such compounds differ only in the nature of the R.sub.2 substituent and the minor structural differences have been found to have very little effect on the isolation procedures, chemical reactivity and biological activity of such compounds.
In addition to these natural avermectins containing the 25-iso-propyl or 25-sec-butyl-substituent, closely related derivatives containing other branched or cyclic 25-alkyl or 25-alkenyl substituents, including those further substituted by heteroatoms such as oxygen, sulfur, nitrogen, and halogen, are known in the literature. These derivatives are obtained through various adjustments and additions to the fermentation procedures as described fully in the European Patent Application EPO 0 214 731.
Avermectins are products of microbial fermentations using the actinomycete Streptomyces avermitilis. These microbes use acetates and propionates as building blocks for most of the avermectin carbon chain, which is then further modified by microbial enzymes to give the completed avermectin molecules. It is known, however, that the carbon C-25 and the 2-propyl and 2-butyl substituents at this carbon are not derived from acetate or propionate units, but are derived from the amino acids L-valine and L-isoleucine, respectively. These acids then have been found to be directly incorporated into the avermectin structures to give the 2-propyl and 2-butyl C-25 substituents, as is reported by Chen et al., Abstr. Pap. Am. Chem. Soc. (186 Meet., MBTD 28, 1983). It was also disclosed in European Patent Application number 0 214 731 that additions of large amounts of other acids such as cyclopentanoic, cyclobutyric, 2-methylpentanoic, 2-methylhexanoic, thiophene-3-carboxylic acids and others to the fermentation broth of S. avermitilis causes the microbes to accept these acids as substitutes and to make small amounts of avermectins containing these acids in form of new C-25 substituents. Examples of such new avermectin derivatives are:
25-(thien-3-yl)-25-des-(2-butyl)-avermectin A2a PA0 25-(cyclohex-3-enyl)-25-des-(2-butyl)-avermectin A2a PA0 25-cyclohexyl-25-des-(2-butyl)-avermectin A2a PA0 25-(1-methylthioethyl)-25-des-(2-butyl)-avermectin A2a PA0 25-(2-methylcyclopropyl)-25-des-(2-butyl)-avermectin A2a PA0 3',3"-Bisdesmethyl-avermectin B1a and B1b PA0 3',3"-Bisdesmethyl-avermectin B2a and B2b PA0 3"-Desmethyl-avermectin B1a and B1b PA0 3"-Desmethyl-avermectin B2a and B2b PA0 3',3"-Bisdesmethyl-25-cyclohexyl-25-des-(2-butyl)-avermectin B2a PA0 3',3"-Bisdesmethyl-25-cyclopentyl-25-des-(2-butyl)-avermectin B2a PA0 3',3"-Bisdesmethyl-25-(3-thienyl)-25-des-(2-butyl)-avermectin B2a PA0 3',3"-Bisdesmethyl-25-(3-furyl)-25-des-(2-butyl)-avermectin B2a PA0 3',3"-Bisdesmethyl-25-(1-methylthioethyl)-25-des-(2-butyl)-avermectin B1a. PA0 R.sub.2 is PA0 R.sub.3 is PA0 R.sub.7 is hydrogen or C.sub.1-6 alkyl, either straight chain or branched; and PA0 R.sub.4 is ##STR4## wherein: R.sub.5 is PA0 R.sub.6 is PA0 A at the 22,23 position represents a single bond and wherein R.sub.1 is hydrogen or hydroxy, or A represents a double bond and R.sub.1 is absent; PA0 R.sub.2 is an alpha-branched C.sub.3 -C.sub.8 alkyl group, an alpha-branched C.sub.3 -C.sub.8 alkenyl group, C.sub.4-6 cycloalkyl, C.sub.4-6 cycloalkenyl, phenyl, or p-fluoro-phenyl; PA0 R.sub.3 is hydroxy or oxime; PA0 R.sub.7 is methyl; PA0 R.sub.4 is ##STR5## where R.sub.5 is PA0 R.sub.6 is PA0 A at the 22,23 position represents a single bond and wherein R.sub.1 is hydrogen or hydroxy, or A represents a double bond and R.sub.1 is absent; PA0 R.sub.2 is 2-propyl, 2-butyl, 2-buten-2-yl, 2-penten-2-yl, 4-methyl-2-penten-2-yl, cyclohexyl, cyclohexenyl, cyclopentyl, cyclopentenyl, phenyl, or p-fluoro-phenyl; PA0 R.sub.3 is hydroxy; PA0 R.sub.7 is methyl; and PA0 R.sub.4 is ##STR6## wherein R.sub.5 is SCOR.sub.6 or S(O).sub.n R.sub.6 wherein n is 0, 1 or 2; wherein: PA0 R.sub.6 is C.sub.1-3 alkyl either straight or branched chain and either unsubstituted or substituted with 1-3 substitutents selected from PA0 4"-deoxy-4"-epi-methylthio-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-4"-epi-methylthio-avermectin B1a/B1b, PA0 4"-deoxy-4"-epi-methylsulfinyl-avermectin B1a/B1b, PA0 4"-deoxy-4"-epi-methylsulfonyl-avermectin B1a/B1b, PA0 4"-deoxy-4"-methylthio-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-4"-methylthio-avermectin B1a/B1b, PA0 4"-deoxy-4"-methylsulfinyl-avermectin B1a/B1b, PA0 4"-deoxy-4"-methylsulfonyl-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-epi-methylthio-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-epi-methylthio-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-epi-methylsulfinyl-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-epi-methylsulfonyl-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-methylthio-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-methylthio-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-methylthio-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-methylsulfonyl-avermectin B1a/B1b, PA0 4"-deoxy-4"-epi-octylthio-avermectin B1a/B1b, PA0 4"-deoxy-4"-octylthio-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-octylthio-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-epi-octylthio-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-octylthio-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-epi-octylthio-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-4"-octylthio-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-4"-epi-octylthio-avermectin B1a/B1b, PA0 4"-deoxy-4"-(2-hydroxyethyl)thio-avermectin B1a/B1b, PA0 4"-deoxy-4"-epi-(2-hydroxyethyl)thio-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-(2-hydroxyethyl)thio-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-epi-(2-hydroxyethyl)thio-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-4"-(2-hydroxyethyl)thio-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-(2-hydroxyethyl)thio-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-epi-(2-hydroxyethyl)thio-avermectin B1a/B1b, PA0 4"-deoxy-4"-(2-hydroxyethyl)sulfinyl-avermectin B1a/B1b, PA0 4"-deoxy-4"-epi-(2-hydroxyethyl)sulfinyl-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-(2-hydroxyethyl)sulfinyl-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-epi-(2-hydroxyethyl)sulfinyl-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-4"-(2-hydroxyethyl)sulfinyl-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-4"-epi-(2-hydroxyethyl)sulfinyl-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-(2-hydroxyethyl)sulfinyl-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-epi-(2-hydroxyethyl)sulfinyl-avermectin B1a/B1b, PA0 4"-deoxy-4"-(2-hydroxyethyl)sulfonyl-avermectin B1a/B1b, PA0 4"-deoxy-4"-epi-(2-hydroxyethyl)sulfonyl-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-(2-hydroxyethyl)sulfonyl-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-epi-(2-hydroxyethyl)sulfonyl-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-4"-(2-hydroxyethyl)sulfonyl-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-4"-epi-(2-hydroxyethyl)sulfonyl-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-(2-hydroxyethyl)-sulfonyl-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-epi-(2-hydroxyethyl)-sulfonyl-avermecti n B1a/B1b, PA0 4"-deoxy-4"-epi-thioacetyl-avermectin B1a/B1b, PA0 4"-deoxy-4"-thioacetyl-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-thioacetyl-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-epi-thioacetyl-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-thioacetyl-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-epi-thioacetyl-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-4"-thioacetyl-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-4"-epi-thioacetyl-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-epi-thiocyanato-avermectin B1a/B1b, PA0 4"-deoxy-5-oximino-4"-epi-thiocyanato-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-thiocyanato-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-5-oximino-4"-epi-thiocyanato-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-4"-thiocyanato-avermectin B1a/B1b, PA0 4"-deoxy-22,23-dihydro-4"-epi-thiocyanato-avermectin B1a/B1b, PA0 4"-deoxy-4"-epi-methylthio-25-des-(2-butyl)-25-cyclohexyl-avermectin, PA0 4"-deoxy-4"-epi-methylthio-25-des-(2-butyl)-25-phenyl-avermectin, PA0 4"-deoxy-4"-epi-methylthio-25-des-(2-butyl)-25-[2-(4-methylpenten-2-yl)]-av ermectin, PA0 4"-deoxy-4"-epi-(2-amino)ethylthio-25-des-(2-butyl)-25-cyclohexen-2-yl-aver mectin, PA0 4"-deoxy-4"-epi-trifluoromethylthio-avermectin B1a/B1b, PA0 4"-deoxy-4"-epi-2,2,2-trifluoroethylthio-avermectin B1a/B1b, and PA0 25-cylopentyl-25-des-(2-butyl)-4"-epi-thioacetyl-avermectin B1a.
Similar experiments producing avermectins "c" and "d" containing as C-25 substituents a 2-pentyl and 2-hexyl group are described by T. S. Chen, et al. in Arch. Biochem. Biophys. 1989, 269, 544-547.
Still additional avermectin derivatives are produced through artificial modification of the fermentation of Streptomyces avermitilis either by addition of metabolic inhibitors such as sinefungin (as described by Schulman et al., J. Antibiot. 1985, 38, 1494-1498) or by mutation of the parent strain (as described by Schulman et al., Antimicrobial Agents and Chemotherapy, 1987, 31, 744-747, and by EP-276-131-A to Pfizer Inc.). Some of these avermectin derivatives are still further modified and are missing one or two of the 3'- and 3"-O-methyl groups (Schulman et al., J. Antibiot. 1985, 38, 1494-1498). Examples of such derivatives are:
The fermentation products have been chemically modified in order to obtain further antiparasitic and insecticidal analogs with improved properties. Publications of such procedures in the scientific and patent literature have been reviewed by Fisher, M. H.; Mrozik, H.; in Macrolide Antibiotics; Omura, S., Ed.; Academic: New York, 1984; pp. 553-606, and by Davies, H. G.; Green, R. H. Nat. Prod. Rep., 1986, 3, 87-121.
For example, a group of semisynthetic avermectin derivatives were obtained by hydrogenating specifically the 22,23-double bond of avermectin B1 giving 22,23-dihydroavermectin B1 derivatives which have very potent anthelmintic and antiparasitic properties. Other examples of semisynthetic avermectin derivatives contain a 8,9-oxide group, a 4-.alpha.-hydroxy or acyloxy group, a 23-keto group, which all are potent antiparasitic and insecticidal compounds.
These compounds may be used as starting materials for the compounds of this invention without further modification, or when containing additional reactive groups, which are not to be modified under the reaction conditions applied, only after protection of such with a suitable protecting group.